#! /bin/bash

val=`expr 2 + 2`;
echo "两数之和为：$val";

a=10
b=20

val=`expr $a + $b`
echo "a+b=$val";

if [ $a == $b ]
then
  echo "a==b";
else
  echo "a!=b";
fi


if [ $a -lt $b ]
then
  echo "a小于b";
else
  echo "a大于b";
fi
